1. Field of the Invention
The invention relates to the field of propulsion systems and, in particular, to a turbojet propulsion system wherein lasers are used to add additional energy to the combustion process.
2. Description of Related Art
Recent Defense Advanced Research Projects Agency (DARPA) advances in the field of Diode Pumped Solid State Laser Technology, specifically Fiber Lasers, have enabled scalable and robust system packaging architectures for operation in harsh environments. These next generation fiber laser systems require minimal thermal management and possess a relatively small footprint within an integrated assembly. The combination of a laser diode pump and an optical fiber gain medium makes possible extremely compact packages suitable for a diversity of applications. State of the art solid-state laser technology comprises three principal components, namely the lasing material (active medium), the optical pump source, and the optical cavity (resonator). The lasing material can be Ytterbium-Yttrium Aluminum Garnet (Yb-YAIG) crystal, or Yfterbium/Erbium-Ytterbium doped optical fiber. The optical pump source (flash lamp, laser diode or fiber laser) adds energy to the lasing material to cause electron collisions, and hence radiation from a laser, by principle of population inversion.
Transmitting laser energy from some platform (ground, airborne, or orbiting) through an optical window to heat a working fluid, has been investigated either theoretically or experimentally by NASA among other organizations. Examples of these types of propulsion systems can be found in U.S. Pat. No. 4,036,012, Laser Powered Rocket Engine Using A Gas Dynamic Window by M. L, Monsler; U.S. Pat. No. 6,459,205, Propulsion System And Method Of Generating Shockwaves by W. Schall, et al.; U.S. Pat. No. 6,488,233, Laser Propelled Vehicle by L. N Myrabo and U.S. Pat. No. 5,152,135, Reflector For Efficient Coupling Of A Laser Beam To Air Or Other Fluids by J. T. K. Because they all utilize external (not on-board) laser systems to generate gas dynamic propulsion, they have limited use and application.
U.S. Pat. No. 6,385,963, Optical System For Generating Endothermic Fuel For Use In A Propulsion System By J. H. Hunt, et al discloses a rocket engine wherein fuel and oxidizer are injected into a thrust chamber and ignited. A laser system is used to heat the fuel to a temperature wherein it dissociates prior to injection into the combustion chamber, thus increasing the energy available to produce thrust. U.S. Pat. No. 5,542,247, Apparatus Powered Using Laser Supplied Energy by B. B. Bushman discloses both rocket engine and turbojet engine concepts wherein the laser is used within the combustion chamber for disassociation of the air molecules, producing pressure waves, consequently providing thrust. However, this latter concept does not address the power required to actuate the laser.
Thus, it is a primary object of the invention to provide a propulsion system wherein lasers are used to provide increased thermal activity in the combustion chamber, thereby causing enhanced combustion and consequently augmenting thrust or power output.
It is another primary object of the invention to provide a turbojet propulsion system wherein lasers are used to provide increased thermal activity in the combustion chamber.
It is a further object of the invention to provide a propulsion system wherein lasers are used to provide increased thermal activity in the combustion chamber wherein the propulsion system provides the power for the laser.